Stabilization of rubber with a mixture of a phenol sulfide and trivalent antimony oxide



Patented Jan. 8, 1952 STABILIZATION OF RUBBER WITH A MIX- TURE OF A PHENOL S-ULFIDE AND TRIVA- LENT ANTIMONY OXIDE Harry E. Albert, Akron, Ohio, assignor to The Firestone Tire dz Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application January 25, 1950, Serial No. 140,555

Claims.

This invention relates 'to thestabilization of rubber with a mixture of a phenol sulfide and trivalent antimony oxide.

This application is a continuation-in-part of my application Serial No. 720,486, filed January 6, 1947 which in turn is a continuation-in-part of my applications Serial Nos. 623,851 and 623,852, filed October 22, 1945. The two latter applications have become abandoned and the first application has matured into U. S. 2,514,193. Those applications relate to the stabilization of rubber with antimony phenol sulfides. The antimony oxide and phenol .sulfides used in the mixtures employed in carrying out the present invention do not react at vulcanization temperatures and the stabilizing action of the mixtures is therefore due to the co-action of the two ingredients.

The antimony oxide is trivalent antimony oxide. The phenol sulfides contain two or more aromatic nuclei. These nuclei may include alkyl or halogen substituents. Phenol monosulfides, disulfides, and polysulfides may be used in the mixture but where discoloration is to be prevented the monosulfides will ordinarily be preferred. The phenol sulfides may be represented by the following formula:

where R, R1 and R2 may be hydrogen, halogen, or hydrocarbon substituents which contain up to eight carbon atoms and may be different or the same in each of the aromatic nuclei; 1: may be an integer from 0 to 3, inclusive, so that there are from 2 to 5, inclusive, aromatic nuclei in the phenol sulfide; and :c may be an integer from 1 to 2 ture may contain as little as parts by weight of either component with 90 parts by weight of the other component. The amount of the mixture used will depend upon the use to which the rubber is to be put and any small amount from one-tenth of a per cent up to about 10 per-cent, for example, may be used.

The mixture of antimony oxide and phenol sulfide stabilizes natural rubber and the synthetic rubbers. It is particularly valuable in the stabilization of the copolymer of butadiene and styrene, known as GR-S. More generally it may be used for the stabilization of the copolymer of (1) any'hydrocarbon conJugated-diene monomer. including butadiene, isoprene, cyclopentadiene, piperylene, dimethyl butadiene, 2-methyl-1,3- pentadiene, etc., and (2) a vinyl aromatic monomer, including, for example, styrene, alphamethyl styrene, nuclear-substituted styrenes, monochloro styrene, dichloro styrene, vinyl naphthylene, vinyl biphenyl, vinyl carbazole, 2- vinyl-5-ethylpyridene, 2-ethyl-5-vinylpyridine, etc. The mixture may likewise be used tut probably with less satisfactory results for. the stabilization of any copolymer of any of the foregoing hydrocarbon conjugated-diene monomers and a monomer having the formula when R is hydrogen, methyl, ethyl, propyl or chlorine, and X is -CN, COR', COOR' or CONH: and R is an alkyl group containing about 1 to 5 carbon atoms. The copolymers of butadiene and acrylonitrile are the best known rubbers of this latter group.

The invention will be illustrated by reference to the stabilization of GR-S by a mixture containing equivalent amounts by weight of diphenol sulfide and trivalent antimony oxide. Two per cent of the mixture was added to a latex of GR-S before coagulation, so that on coagulation the components of the mixture were thoroughly dispersed throughout the copolymer. GR-S copolymer was similarly prepared by coagulation of GR-S latices containing two per cent of phenylbeta-naphthylamine and a widely used commercial stabilizer which is identified herein as stabilizer No. 1. The three samples of copolymer thus prepared were dried for 20 hours at. C. The dried samples were compared to notegauy discoloration which had taken place and for evidence of deterioration. The samples were then heat-aged at C. and comparative tests were made after one day, two days and four days to note any discoloration and evidences of deterioration. The results arehbcorded in the following table:

TABLE I copolymer aging teat Equivalent amounts of di 'henol Stabilizer Phenyl-betado and No. 1 naphthylaantimony mine oxide After dryin 20 hours at 75 0.:

Color Light gray- Bluish gray... Red-brown.

rown. Hand Test.--.. No deterlora- No deteriora- No deteriotion. tion. ration. Heat-aging at 110 v the da 1 1 Light browm- Brown Brown. Band Test. No change Very slightly Nochange.

so up.

Two Da s Colo? Light brown Darkbrown... Dark brown. Hand Test. No change Somewhat set Veryslightly up. set up. Four'D s col r Light brown.. Darkbrown... Darkhrown. Hand Test. Slightly set Setup Somewhat up. set up.

The sample containing the mixture of antimony oxide and phenol sulfide discolored less than the commercial stabilizers and deteriorated less quickly. In fact, after four days aging the sample containing the mixture still showed little evidence of deterioration.

Portions of the unaged copolymer containing the mixture of antimony oxide and phenol sulfied', and that containing stabilizer No. 1, were then compounded according to the following iormula:

Parts by weight C opolymercontaining 2% stabilizer 100.00 Coumarone resin 10.00 Accelerator -1 1.10 Wax 2.00 Magnesium oxide 8.00 Zinc oxide 100.00 Ultramarine blue 0.10 Titanium dioxide 30.00 Insoluble sulfur 4.00

The different samples were each cured at 300 F. for 30, 50 and '10 minutes respectively. The values obtained for the physical properties of the various stocks were averaged and are recorded in the following table. The values recorded for the aged stock were obtained on the samples after aging four days in a forced circulation oven at 212 F.

In a further test the unaged white vulcani- Mixture of equivalent amounts Stabilizer N o. 1

TABLE III Artificial exposure tests Fadeometer at G. E. Sunlamp at 125 F. 7 inches Antioxidant 5 Hours 8 Hours 16 Hours Mixture oi eqniva- White. White. Ten

lent amounts of antimony oxide and diphenol sulfide Tan... Light brown Tan... Light brown Natural exposure 2 months in Florida (February- April) 2 Months in Florida+2 Months in Akron (May-July) Antioxidant White Very slightly disoi' antimony oxide and dicolored phenol sulfide Light cream.

Stabilizer No. 1 Tan The above tests are illustrative.

What I claim is:

1; Rubber-like copolymer of a hydrocarbon conjugated-diene monomer and vinyl aromatic monomer stabilized with a relatively small amount of a mixture of trivalent antimony oxide and a phenol sulfide of 2 to 5 aromatic nuclei of the class in which the nuclei are unsubstituted, those which are halogen substituted, and those which are substituted with hydrocarbon groups of 1 to 10 carbon atoms, which mixture contains at least 10 parts by weight of the one component and up to parts by weight of the other component.

2. Cured rubber-like copolymer of butadiene and styrene stabilized with a relatively small amount of a mixture of trivalent antimony oxide and a phenol sulfide having 2 to 5 aromatic nuclei of the class consisting of those which are unsubstituted, those which are halogen substituted and those which are substituted with hydrocarbon substituents of 1 to 10 carbon atoms, the mixture containing at least 10 parts by weight of one component and up to 90 parts by weight of the other component.

3. The process of curing rubber-like copolymer of butadiene and styrene which comprises curing the same with sulfur in the presence of a rela-.- tively small amount of a mixture of trivalent antimony oxide and a phenol sulfide having 2 to 5 aromatic nuclei of the class consisting of those a HARRY E. ALBERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,175,082 Hagen et a1 Oct. 3, 1939 5 2,244,021 Rosen et a1. June 3, 1941 2,364,338 Beaver Dec, 5, 1944 OTHER REFERENCES Werner: Esch. Farben-Chem., 10 pp., 129-130, 10 1939; C. A. 34, 3133 (1940). 

1. RUBBER-LIKE COPOLYMER OF A HYDROCARBON CONJUGATED-DIENE MONOMER AND VINYL AROMATIC MONOMER STABILIZED WITH A RELATIVELY SMALL AMOUNT OF A MIXTURE OF TRIVALENT ANTIMONY OXIDE AND A PHENOL SULFIDE OF 2 TO 5 AROMATIC NUCLEI OF THE CLASS IN WHICH THE NUCLEI ARE UNSUBSTITUTED, THOSE WHICH ARE HALOGEN-SUBSTITUTED, AND THOSE WHICH ARE SUBSTITUTED WITH HYDROCARBON GROUPS OF 1 TO 10 CARBON ATOMS, WHICH MIXTURE CONTAINS AT LEAST 10 PARTS BY WEIGHT OF THE ONE COMPONENT AND UP TO 90 PARTS BY WEIGHT OF THE OTHER COMPONENT. 